1,2-Propanediol-linked chiral symmetric and non-symmetric liquid crystal dimers containing trifluoromethyl

ABSTRACT

Four symmetric and non-symmetric chiral liquid crystal dimers containing trifluoromethyl groups, termed as TFBA-PD-TFBA, UEBBA-PD-TFBA, UEBA-PD-TFBA and UEA-PD-TFBA, respectively, have been synthesised and characterised. UEA-PD-TFBA exhibited chiral nematic phase, whereas the other three dimers displayed chiral smectic A phase. X-ray diffraction (XRD) has revealed the structure of the smectic A phase for TFBA-PD-TFBA to be intercalated, whereas that for UEBBA-PD-TFBA and UEBA-PD-TFBA to be monolayer and interdigitated, respectively. In addition, the weaker peak corresponding to a shorter layer spacing was observed for UEBBA-PD-TFBA and UEBA-PD-TFBA. Considering the results of XRD measurements and computer simulations, the structural model corresponding to the shorter layer spacing is assigned as horseshoe-like shape. The absence of smectic behaviour for UEA-PD-TFBA reveals that the weaker aromatic–aromatic interactions cannot stabilise the smectic A phase.

GRAPHICAL ABSTRACT

KEYWORDS:

• Chiral liquid crystal dimer
• trifluoromethyl-based mesogen
• intercalated smectic structure
• symmetric
• non-symmetric

Disclosure statement

No potential conflict of interest was reported by the authors.

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Additional information

Funding

This work was financially supported by the Fundamental Research Funds for the Central Universities [N130205001]; Science and Technology Bureau of Shenyang [F14-231-1-05]; the National Natural Science Fund of China [51273035].